I. Field of the Invention
This invention relates generally to permanent magnets designed to be deposited in a stomach of a ruminant animal, such as a dairy cow, for attracting, collecting and holding sharp ferrous metal objects which may be ingested by the animal during grazing to prevent hardware disease and inhibit sharp objects from passing through the digestive system of the animal. More particularly, the invention pertains to an improved construction of such a permanent magnet device that enhances the magnetic force of attraction of the assembly for a given size and which is better capable of withstanding the harsh environment in which the magnet is used.
II. Discussion of the Prior Art
It is known that when certain ruminant animals are grazing, they will frequently pick up and ingest with their feed bits of metal, such as barb wire, baling wire, nuts and bolts, nails and other metal fragments present in a pasture, stall or feed lot. If such sharp metal objects are allowed to pass through the animal's digestive tract, series injury, hardware disease and even death to the animal can result. It has been the practice for some time now to place one or more permanent magnets in the animal's stomach so that as ferrous metal objects are later ingested by the animal, they will be attracted to the magnet and will adhere thereto rather than passing through the animal's digestive system. In a recent agricultural study, it was found that through consistent installing of cow magnets in diary cows, a 90-98% success rate was achieved in the prevention of hardware disease.
In the Fujisawa Pat. No. 4,283,698, there is described a magnetic device comprising a plurality of cylindrical ceramic magnet segments of cylindrical shape which are arranged in a stacked relationship with one another with adjacent magnetic poles of like polarity adjacent one another and with disks of a soft magnetic steel material interposed therebetween. A longitudinal bore passes through each of the stacked members whereby a first post having a hemispherically-shaped end cap can be inserted through the stack to mate with a second hemispherically-shaped end with the two being joined by a screw-type fastener. A problem has existed with the product made in accordance with the Fujisawa patent. Examination of cow magnets removed from the stomachs of the animals, following slaughter, has revealed that the individual magnetic cylinders and spacers have become detached from one another due to breakage of the plastic center post or failure of the screw threads used to hold the end cap to the mating post.